Some userspace programs got problems with the 2.6.x→3.x kernel numbering transition. To prevent the need to fix everything at once, the Fedora developers decided to ship 3.x kernels as 2.6.4x on Fedora 15 Lovelock and use the correct numbering scheme on Fedora releases ≥16 Verne.

This kernel version numbering hack makes some problems with the current VirtualBox 4.1.6 on Fedora 15: /etc/init.d/vboxdrv setup exits with an error (/var/log/vbox-install.log says that recompiling VBoxPci-linux.o failed). The reason is simple: A check thinks that the running kernel 2.6.41.1 is older than 3.1. Therefore the wrong header file gets included (asm/amd_iommu.h instead of linux/amd-iommu.h).

@dutchhome: Come on, it does not matter. This it is just a local(!) hack to get things working again on the specific system you are running. It does not get redistributed. BTW: KERNEL_VERSION(2, 6, 41) is not a “much better” or general solution, too. E.g. it would break things on a 3.0 kernel machine.